Explain how a reflex action occurs

Reflex actions are automatic responses to stimuli i.e. a change in an environment.A receptor first detects a stimulus such as heat, its function is to convert this stimuli energy in this case heat into an electric signal or impulse. A sensory neurone which is connected to this receptor will then conduct this impulse to the spinal cord. The impulse will then encounter a gap/junction between the end of the sensory neurone and a new neurone known as the relay neurone in the spinal cord. This junction is referred to as the synapse, and the impulse will be transmitted across the synapse using neurotransmitters. Following conduction along the relay neurone there will be another synapse with the motor neurone which is connected to the muscle. The impulse is then transmitted along the motor neurone to the effector (muscle or gland) which will carry out a response. In this case a muscle can contract to withdraw the hand from heat.